It was the first time a president has called for ending the endowments. They were created in 1965 when President Lyndon B. Johnson signed legislation declaring that any “advanced civilization” must fully value the arts, the humanities, and cultural activity.

While the combined annual budgets of both endowments — about $300 million — are a tiny fraction of the $1.1 trillion of total annual discretionary spending, grants from these agencies have been deeply valued financial lifelines and highly coveted honors for artists, musicians, writers and scholars for decades.

Nothing will change for the endowments or other agencies immediately. Congress writes the federal budget, not the president, and White House budget plans are largely political documents that telegraph a president’s priorities.

Yet never before have Republicans, who have proposed eliminating the endowments in the past, been so well-positioned to close the agencies, given their control of both houses of Congress and the White House, and now the president’s fiscal plan. Reagan administration officials wanted to slash the endowments at one point, for instance, but they faced a Democratic majority in the House (as well as Reagan friends from Hollywood who favored the endowments).

As for 2017, it is unclear whether Republicans who are friendly to the endowments will fight their own party’s president on their behalf. Mr. Trump went ahead with the proposal even though his daughter Ivanka is a longtime supporter of the arts, and Karen Pence, the wife of Vice President Mike Pence, has been a staunch advocate for art therapy for years, being a painter herself.

Who benefits from these endowments? Well, you do, for starters—assuming you’ve ever read a history book or novel, visited a museum or historic site, used a library or website to research your genealogy, watched a documentary, attended an author’s talk, etc., etc., etc.

Would killing these endowments save money? Yeah, something like 0.006% of federal spending. That’s not hyperbole, by the way; that’s literally how much of the federal budget the NEH and NEA accounted for last year. Why anyone would want to kill agencies that do so much for so little is beyond me.